LONDON, December 29 (Reuters) - Companies seeking to "bulk up" to offset the uncertainty caused by Britain's looming EU exit helped to spur a near doubling of domestic mergers and acquisition activity this year, according to Thomson Reuters data.

GVC's takeover of Ladbrokes Coral was one of the biggest deals of the year. Jeff J Mitchell/Getty Images The volume of UK domestic deals surged to $68 billion (£50.3 billion), from $34.3 billion in 2016, as the number of deals between British groups jumped from 1,480 to 1,681, the highest level since 2008, the data show.

It comes against a backdrop of often fractious Brexit negotiations between London and Brussels this year, talks that are yet to provide businesses with clarity about Britain's future relationship with Europe.

Bosses at British companies have also been eyeing new U.S. President Donald Trump, whose decisions have repercussions for businesses around the world.

'Tomorrow's leaders'

"At the beginning of 2017 there were a lot of questions about what was going to happen to the M&A market, given the global uncertainty caused by Brexit and the new U.S. president," said Nick Cline, a London-based M&A partner at law firm Latham & Watkins, who said the uncertain environment had acted as a driver for some deals rather than stifling activity.

"There are a lot of corporates out there in the UK and Europe who are seeing the changing landscape and as a result are even more focused on what they're going to do to be tomorrow's leaders."

The jump in domestic deal-making contrasted with falls in both inbound and outbound UK M&A volumes, the data show, with the former slipping 12.9% to $115.1 billion and the latter down 9.4% to $112.5 billion.

That meant overall M&A volumes with any UK involvement dipped 0.7% to $375 billion, a softer decline than the 1.4% slide in global deal volumes to $3.5 trillion, according to the data.

'The Brexit climate which is prompting companies to bulk up'

Philip Noblet, HSBC's co-head of global banking in the UK, said that "a lot of the obvious sector consolidation deals that people expected to happen" were struck this year and were "driven by the Brexit climate which is prompting companies to bulk up."

However, a dearth of blockbuster deals meant that overall M&A volumes involving any British companies remained much lower than in 2015, when they totalled $605.5 billion, swelled by Anheuser-Busch Inbev's $110 billion acquisition of FTSE 100 brewer SABMiller and Royal Dutch Shell's $53 billion tie-up with BG Group.

"It's hard to see how any more of the really big deals are going to happen going forward without there being quite significant competition issues," said Noblet.

Potential British government scrutiny of the deal was a concern raised during talks between the two companies, a person familiar with the matter told Reuters at the time.

Since Theresa May became prime minister in July 2016, Britain has taken a more cautious approach towards foreign acquisitions of British assets.

In October, the government proposed new rules to give it more say over deals in the defence and technology sectors, although Cline said the government's change of tack had not represented "a step-change this year in the way the UK looks at deals".

He said: "Occasionally a transaction comes up where there's a question about UK government intervention."

Cline forecasts that British M&A activity will remain strong in 2018, while Jan Skarbek, managing director of UK banking and broking at Citigroup, also thinks there will be an increase.

"Organic growth is very difficult in this environment and staying still is not an option for many companies," he said. "So I think there will be more deals next year, despite the geopolitical uncertainty."